HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ANALYSIS OF MELATONIN IN HUMAN PLASMA AND RABBIT SERUM WITH ONLINE COLUMN ENRICHMENT

This paper describes the development of a simple and sensitive analyti cal method for the quantification of melatonin in human plasma and rab bit serum, using standard analytical equipment and on-line column enri chment without prior extraction, clean-up or derivatization. The analy tical procedure was found to be accurate, precise and linear. For huma n plasma, the accuracy was 101% (range 89-106%), and the mean precisio n was 5% (range 2-9%) for all concentrations (0, 2, 10, 50 and 200 ng/ ml) tested (n =6). The accuracy in rabbit serum was 101% (range 90-112 %), and the mean precision was 13% (range 8-19%) for all concentration s (0, 2, 10, 50, 200 and 500 ng/ml) tested (n =6). The retention time of melatonin was about 8 min and the total recoveries were found to be approximately 65 and 85%, respectively, for human plasma and rabbit s erum. The Limit of detection was found to be lower than 1 ng/ml for hu man plasma and around 2 ng/ml for rabbit serum. The method is, therefo re, found to be suitable for melatonin bioavailability studies in rabb its and presumably also in humans. (C) 1998 Elsevier Science B.V. All rights reserved.